Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN2 from the interface PCB

Measurement:

Test 1:
Measure the resistance between Pin 7 (Blue) and Pin 8 (Brown) on connector CN2.
Resistance should be greater than 1M Ohm (or O.L.)
Test 2:
Measure the resistance between Pin 8 (Brown) on connector CN2 to a suitable earth point.
Resistance should be greater than 1M Ohm (or O.L.)